A known self-testing method (Koenemann, B.; Mucha, J.; Zwiehoff, G.; Built-In Logic Block Observation Techniques; IEEE Int'l Test Conference, 1979) uses linear feedback shift registers to produce real-time test stimuli and to compress the test responses. In this case, the data flow is observed at internal test points of complex digital circuits. Since the reaction of the circuit to the test stimuli is detected only at the primary outputs of the circuit in this method, bridge faults cannot reliably be identified, specific stuck-at faults can be identified only with difficulty and redundant stuck-at faults cannot be identified at all. In other known self-testing methods (Chang, T.; Wang, C.; Hsu, J.; Two Schemes for Detecting CMOS Analog Faults; IEEE Journal of Solid-State Circuits, Vol. 27, No. 2, Feb. 1992; or Favalli M. et al.; Novel Design for Testability Schemes for CMOS IC's; IEEE Journal of Solid-State Circuits, Vol. 25, No. 5, Oct. 1990), built-in current sensors are used for sensing the static current consumption (Iddq monitoring).